1. Field of the Invention
The present invention relates to a battery monitoring apparatus for monitoring the states of unit cells constituting a battery pack.
2. Description of Related Art
The voltages of unit cells constituting a battery pack may vary from one another due to repetition of charge and discharge. In this case, unit cells undergoing overcharge or overdischarge may be damaged.
Accordingly, it is common that such a battery pack is provided with a battery monitoring apparatus for monitoring the states of the unit cells constituting the battery pack. The battery monitoring apparatus is connected with the unit cells through wires and connectors to measure the terminal voltage of each unit cell from the voltage between a corresponding adjacent two of the wires.
The battery monitoring apparatus includes an equalizing unit constituted of equalizer switches and resistors for discharging each of the unit cells by short-circuiting the corresponding adjacent wires. The equalizing unit discharge a unit cell whose terminal battery is excessively high to remove the variation in terminal voltage among the unit cells.
However, the wires and the connectors which connect the battery pack to the battery monitoring apparatus deteriorate after long time use due to repetition of voltage measurement and equalization, or after long time non-use. If the wires or connectors deteriorate, since their electrical resistance increases, the accuracy at which the voltage measurement or equalization is performed may be adversely affected.